

b =''
if b:
    print("b")
else:
    print("b为空")

c=[]
if c:
    print("c")
else:
    print("c为空")


d=()
if d:
    print("d")
else:
    print("d为空")


f= {}
if f:
    print("f")
else:
    print("f为空")


if 10<20 and 20<30:
    print("10<20 and 20<30")